Cannot view/edit site on local network

[igi2011]

Hi,
We recently installed 4 zen cart stores on a dedicated LAMP server.

Two of them are rebuilds of existing sites we were previously hosting elsewhere (one on 1.5 and one on 1.39)

Prior to the domains being changed I was accessing them via the server's IP on our LAN. I had the servers in each store's includes/configure.php and MY_ADMIN/includes/configure.php files pointing to this IP address. As soon as we redirected the domain names to our server I changed the configure files so they were pointing to the web addresses.

Now I can see both sites... but only if I'm not accessing them on the network! Because the IP address of the server is the same as our router, if I type in the url I get diverted to the router's login page.

I can see the sites by typing in the server's name on the network, but no images are displayed... and the admin pages aren't accessible either. So I assume this is to do with the paths in the configure.php files which I had to change to the stores' web addresses - I can see the other two sites on the server with no problems as they're not yet live.

I know this is probably something to do with our router rather than Zen Cart itself, but just wondered if anyone else has had this problem and how it can be solved.